In grinding or pulverizing coal to be burned in furnaces for generating steam, it is common to use a rotating ring or bowl, and a plurality of cooperating members, such as rollers or balls. In the the past, the bowl has been driven by a single electric motor. Because of the demand of higher capacity, it is not uncommon for the grinding bowl to approach 10 feet in diameter, and having a vertical load of 500,000 pounds. These large loads require a complex and heavy gear reduction drive between the electric motor and the central driven shaft of the bowl. Depending on the type of coal being pulverized, and the degree of fineness of the finished product desired, it might be desirable to be able to change the speed of rotation of the bowl. This presents problems when there is a single electric motor direct-coupled for driving the bowl.